Statistics Module 2

A new drug designed to prevent exacerbations of genital herpes undergoes a clinical trial. One hundred patients are given the new drug. During a three month period, 10 of the patients have an episode of genital herpes.

In the control group there are 300 patients who are given a placebo. In this group 50 people have an exacerbation during the same time period.

What is the relative risk of having an exacerbation of genital herpes whilst taking the new drug?

A cohort study is being designed to look at the relationship between smoking and breast cancer. What is the usual outcome measure in a cohort study?

Which one of the following statements best describes a type II statistical error?

Which one of the following statements regarding the power of a study is correct?

A study looks at the chance of having a myocardial infarction (MI) in patients with known ischaemic heart disease.

Group A are given standard treatment. After 5 years 20 of the 100 patients have had a MI.

Group B have standard treatment plus a new cardiac drug. After 5 years 10 of the 60 patients have had an MI.

What is the odds ratio of having a MI whilst taking the new drug compared to those who do not?

A study looks at whether golf actually increases the risk of medial epicondylitis. Sixty people who regularly play golf are matched to sixty people who do not play golf. Thirty of the golfers had developed medial epicondylitis at some point compared to ten of the non-golfers.

What is the odds ratio of developing medial epicondylitis for people who play golf?

Which one of the following statements regarding relative risk is correct?

A study is to be performed to assess whether the combined oral contraceptive pill is protective against pelvic inflammatory disease.

What is the most appropriate type of study design to provide robust evidence?

A new drug is trialled for the treatment of lung cancer. Drug A is given to 500 people with early stage non-small cell lung cancer and a placebo is given to 450 people with the same condition. After 5 years 300 people who received drug A had survived compared to 225 who received the placebo.

What is the number needed to treat to save one life?

A new blood test to screen patients for heart failure is trialled on 500 patients. The test was positive in 40 of the 50 patients shown to have heart failure by echocardiography. It was also positive in 20 patients who were shown not to have heart failure.

What is the positive predictive value of the test?

A study is performed looking at the chance of stroke in high-risk patients taking a new oral antithrombotic drug compared to warfarin. The following results are obtained:

What is the relative risk of having a stroke within a 3 year period for patients taking the new drug compared to warfarin?

Which one of the following statements best describes a type I statistical error?

A new test to screen for ovarian cancer in patients with a positive family history is tested on 920 patients. The test is positive in 16 of the 20 patients who are proven to have ovarian cancer. Of the remaining patients, only 10 have a positive test.

What is the negative predictive value of the new test?

A cohort study is designed to look at the association between working long hours and blood pressure.

The following results are obtained after 10 years of follow-up:

What is the odds ratio of developing hypertension if you work more than 40 hours/week compared to people who work less than 40 hours/week?

Which one of the following statements regarding odds and odds ratio is correct?

What is the correct formula to calculate the positive predictive value?

A randomised controlled trial is performed to look at a new drug to prevent hip fractures in postmenopausal women. Group A consists of 1,000 women who take the new drug whilst group B contains 1,400 women taking a placebo. The hip fracture rate in group A is 2% and in group B is 4%.

What is the number needed to treat to prevent one hip fracture?

A rapid urine screening test is developed to detect Chlamydia. A trial involving 200 men and women is performed comparing the new test to the existing NAAT techniques:

What is the negative predictive value of the new test?

A new screening test is developed for colorectal cancer. It is a blood test which detects a protein; the higher the level of the protein, the more likely a patient is to have colorectal cancer. If the cut-off for a positive test is increased, which of the following statistical value would also be increased?

Which one of the following statements regarding the use of the p-value in statistical hypothesis testing is correct?

A study looks at the use of amoxicillin in the treatment of acute sinusitis compared to placebo. The following results are obtained:

What is the odds ratio a patient achieving resolution of symptoms at 7 days if they take amoxicillin compared to placebo? 

A study is performed comparing two chemotherapy regimes for patients with small cell lung cancer. The end point of the study is survival time. Which one of the following types statistical measures is it most appropriate to compare survival time with?

A randomised controlled trial compares two drugs used in the initial management of rheumatoid arthritis. After being assigned to the randomised groups a number of patients drop out due to adverse effects of the medication.

How should the data be analysed?

An endocrinologist performs a study to assess whether a patient’s HbA1c level is correlated to their LDL level. Assuming both HbA1c and LDL are normally distributed,

Which of the following statistical tests would be appropriate?

You are asked to design a study to assess whether living near electricity pylons is a risk factor for childhood leukaemia.

What is the most appropriate type of study design?

A study looks at whether a new oral treatment for patients with heart failure can prevent hospital admissions.

When reviewing the data, how should it be decided if the test was statistically significant?

A disease has an annual incidence of 15 cases per 100,000. The mean survival after diagnosis is five years.

What is the best estimate of the prevalence of this disorder?

Securing informed consent prior to including a patient in a clinical trial for a new anti-hypertensive medication primarily adheres to which fundamental ethical principle?